diff --git a/src/PatchOutput.hs b/src/PatchOutput.hs
index 3351073cb..928d32a89 100644
--- a/src/PatchOutput.hs
+++ b/src/PatchOutput.hs
@@ -5,5 +5,7 @@ import Diff
 patch :: Diff a Info -> String -> String -> String
 patch diff sourceA sourceB = mconcat $ hunks diff sourceA sourceB
 
+data Line = Insert String | Delete String | Context String
+
 hunks :: Diff a Info -> String -> String -> [String]
 hunks diff sourceA sourceB = []